340 camshaft question, yea another one.

159 is just right, I wouldn't spend the time it takes, to change it. Your butt-dyno will never feel it. But if it pushes the engine over the limit into 93 gas, you will sure notice that. A year from now after you have solved all your issues, and if you need something to do, then maybe you could think about it.
Besides it's just a calculator.Your results may vary,lol

Very few guys here push over 8.5 with aluminum heads. I run 8.6 on 87E10,fulltime with aluminum heads. So I know I left some on the table. But even a full point, they say translates to just a 4% power increase or maybe less. 4% of 400 is 16 hp.And I have heard only one fello here state that he runs close to 9.5Dcr with aluminum. I don't recall the exact number, but Ima thinking I would max out at a half a point more at 9.1Dcr, which might translate to 2% x 400=8hp
Now the truth is 400 hp in a streeter can spin the tires, big tires, the biggest tires you can fit into the stock wheelhouses to waaaay past the hiway speedlimit. Am I missing those 8 hp? Not even one tiny bit.
Advancing your cam 2*, IMO,and not to be a dick, is a total waste of time,been there/done that.
So lets say I could run a half point more on 91, or 9.0-Dcr. They say aluminum can run a half point more than iron. That, then would agree with what your research says, namely that iron heads can top out at 8.5. It doesn't mean you gotta run there. What's the price difference in your neighborhood between 87 and 91, and how many more dollars are you gonna burn through in a year. Only you can justify the cost. And what if the price of gas doubles overnight?
Your 274* can make a lot of power in your combo. With the right gears and TC, you too can spin the tires all the way to shift-rpm in first and maybe in second too. In a few weeks or by spring time, these days will be but a fading memory.
And I guarantee that a 2800TC or better will put the biggest smile on your face. With a 340, Ima thinking, maybe a lil more,even.lol